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Leiden University launches Earth Observation platform

A new online platform makes it possible to estimate the state of agricultural crops and nature area’s around the world. This enables scientists and other users to consistently combine observations of different satellites for the first time.

The platform is called MULTIPLY and was launched in November by the Institute for Environmental Sciences (CML) of Leiden University. For 8 years, researchers from CML worked together with European partners to develop the platform.

Information of multiple satellites

The platform is unique because it combines the information of multiple satellites with varying resolutions and information, instead of using only one individual satellite. This enables MULTIPLY to generate breakthrough information on vegetation and soil moisture.

This data is crucial for different applications such as mapping evapotranspiration during droughts, monitoring declining trends of biodiversity, and quantifying ecosystem services.

Oil-palm plantations

Researchers of the CML have used the platform to quantify the impact of oil-palm plantations in Northern Borneo on biodiversity for the first time using earth observation data. The high resolution of the platform data enabled them to distinguish between the different land uses. The study confirmed a significantly lower biodiversity for the Northern Borneo oil palm plantations, indicating higher risks to ecosystem services.

Currently, the MULTIPLY platform has only been made available to scientists for the purpose of testing it on their own research. During this trial-period, these scientists can explore the benefits of the novel approach, but also provide feedback on how well the earth observation information matches ground measurements. Next to these studies, MULTIPLY will further expanded to even more satellites. Afterwards, the platform will be delivered to the European committee which will allow this service to be available to the general public.

City of Toulouse in Southern France with surrounding agricultural fields. Captured on 10 July 2017 by Sentinel-2 and processed by ESA.

Climbing towers in Finland, the Netherlands, and recently in Ghana, PhD candidate Amie Corbin is crossing borders to collect essential data on vegetation for the MULTIPLY platform. For her research at the Institute of Environmental Sciences at Leiden University, she studies the ecologically important plant traits that can be measured from space.

In order to model data and create earth observation products with the MULTIPLY platform, prior knowledge on the vegetational variables is needed. Corbin collects this knowledge. “I focus on variables that can be both physically observed from space and are ecologically relevant. These variables can be indicators for vegetation health, like chlorophyll and leaf water content.”

Most measurements of plant traits that are currently available are from the peak moment of its growing season. Corbin tries to fill in the knowledge gaps. “By measuring traits of plants at different moments of the year I try to get a grip on year-round phenology,” Corbin explains. “This gives us a better understanding of whether some characteristics are trade-offs or if they are consistent throughout the year.”

Challenges in the fieldCorbin collects measurements from three different types of vegetation: mixed forest in Finland, coniferous forest in the Netherlands and tropical forest in Ghana. “We try to discover how different characteristics from plants are related to each other and how this relationship changes over time, at different latitudes.”

Using a field spectrometer, Corbin measures the reflectance of light. This is similar to how satellites measure reflected radiation from space. But the field measurements result in a higher resolution. “To measure the reflectance, one sensor was placed at the top and one at the bottom. The more plants there are, the less of the light that can be used for photosynthesis will make it to the ground level. Based on this difference we can measure the Leaf Area Index, the amount of leaf area,” Corbin explains.

Collecting the measurements and samples was challenging. “The observation tower that we had to climb to take the samples and collect measurements was quite high, around 30 meters. I was a bit scared to climb the tower and enter the platform at the top, which was quite small,” Corbin admits. Fortunately, she was accompanied by a local guide and an expert tree climber who helped her out. “Our hosts in Ghana from the Forestry Research Institute of Ghana were great.”

The fieldwork was done every two weeks at the same location. “Because the sampling is destructive, and two weeks is enough to let the plants live,” Corbin explains. “Also, it is a lot of samples to process each time.”

Convenient collaborationsA big challenge Corbin encounters during her research is the clouds. Because clouds influence her imagery. “As a person who does not like the heat I am glad when a cloud shows up but as a scientist I really need them to be gone,” says Corbin. Fortunately for her, there are other researchers in the MULTIPLY team who atmospherically correct the images.

Corbin is enthusiastic about the collaborations within the MULTIPLY project and the platform that is being built. “I like that we collaborate not only with other universities but also with big companies. This is really helpful in creating an easy to use platform for remote sensing imagery.”

At certain points during a Horizon 2020 Research & Innovation Action, the project consortium meets for a review meeting. Together with the project officer of the European Commission and with an external reviewer they review the progress of the project. For the MULTIPLY project, on the 28th and 29th of Augustus, one of these review meetings took place at the Tartu Observatory in Estonia.

“It was a really nice and constructive meeting where we could present the current state of the project to the reviewers,” says Dr. Lea Hallik, team member of MULTIPLY and researcher at the University of Tartu. “As we are now finalizing the tests of the beta version of the platform, they were happy with our progress.”

Different types of users“An interesting discussion was about how the platform should be accessible for two types of users. On the one hand, the more technical programmer that wants to create and improve products using satellite data. On the other hand, the earth observations consultants who are less technical and want to access only the end products. This is challenging and something we will have to work on during the next months.”

There was also time for some social activities like a nice tour along the visitor center and the space technology laboratory. “The location was great. It is in a beautiful green setting, 20 kilometers away from the city Tartu and its light pollution.”

MULTIPLY consortium members at the Tartu Observatory

From local to globalHallik and her colleagues from Tartu University, study what kind of plant traits can be measured with satellites. Therefore, she collected data in the field on traits of both evergreen and deciduous trees during the past two summers. With this knowledge, she can validate the measurements from satellites. “I like that we, as a small research group, can contribute with local field measurements to such a big project.”

“In Estonia, we have six towers where you can reach the highest leaves of the trees. There we sample and measure leaf traits like reflectance, transmittance, pigment content, dry mass area, and water content. Because natural vegetation is very complex, especially in a forest, with multiple species and different vegetational layers, satellite data can also be challenging,” Hallik explains. “It is important to understand these time series of forest leaves because an important aim of MULTIPLY is to create time series and make seasonal changes visible.”

Amie Corbin is a PhD student at Leiden University who develops vegetation priors for the platform. From June to Augustus she will be in the Kogyae Strict Nature Reserve in Ghana to collect data. You can follow her adventures through her website.

Team members from Leiden University participated in the “Night of Arts & Science”, on the 16th of September in Leiden. Together with other staff members from the CML, Joris Timmermans, Leon Hauser, and Amie Corbin created “Viewing Beyond”. Using remote sensing technology in several interactive exhibits, they opened the visitors their eyes and let them view beyond the capabilities of the human eye.

Team member Esther Philips: ‘Considering that for most people remote sensing is probably quite unknown, we agreed that it would be really interesting to bring this emerging technology to the masses.’

Using cardboard VR glasses, people could experience how animals see the world. With their left eye, they saw as a human and with their right eye as another animal species, like a bee, a shark, or an eagle. The visitors explored a world that is usually hidden from human eyes.

With a living experiment, visitors observed how remote sensing technology works. Using spectrometers, the reflected light from different types of plants was measured and broadcasted live on a screen. The visitors learned how different plants and different conditions, like varying moisture content or a nitrogen deficiency, yield different outputs.

To discover the various possibilities of remote sensing research, some examples were shown in a slideshow on a screen. For example, how thermal imagery was used to map hurricane Irma and night observations are used to monitor the world light pollution. This last subject was further explained in the final part of the experience.

To make people aware of light pollution, people could see the light pollution on a special nighttime globe. Also, visitors could ‘join the dark side’ and contribute to citizen science projects on light pollution. One of these was created for the festival. Visitors could download a lux meter app and search for the darkest spot in the botanical gardens. By handing in their data they could win a price.

With Viewing Beyond visitors viewed the world beyond their eyes and shared and discussed their experiences and views on research with scientists. This expanded the knowledge of both the visitors as the participating scientists, hopefully leading to a brighter future with darker nights.

A comprehensive field campaign is conducted by the Ludwig-Maximilians-Universität München (LMU) to collect in situ information for the validation of satellite-based retrievals of land surface parameters. These measurements will be used within MULTIPLY to validate the retrieval results of the MULTIPLY platform.
“Our campaign will last for the entire vegetation period in 2017 and collects data from a variety of different land cover types and different soil conditions”, says MULTIPLY team member Prof.dr. Alexander Loew.

During the LMU campaign essential characteristics of vegetation and plant conditions are collected, like e.g. information about vegetation biomass and water content as well as the soil moisture content. In addition, ground-based measurements of the surface radiation fluxes and spectral properties of the plants are collected. The LMU team goes into the field on a regular basis during COPERNICUS SENTINEL satellite overpasses.

ADAS, Assimila and UCL are using the thinking from MULTIPLY to develop the concept of a ‘Crop Intelligence System’ that could provide information to growers on crop growth and performance. The team won an Innovate UK feasibility study under the Satellites for Agri-Food programme. The project started in July 2016 and runs for twelve months. It aims to examine both the technical and commercial feasibility of generating ‘canopy curves’ on a field by field basis for all fields within a region, or country, allowing comparisons of crop performance between fields, farms, years, soils and management practices.

By integrating with soil and weather datasets it should be possible to provide a dashboard for crop growth. Giving information on light and water resources available and captured in each field. This would be an invaluable tool in the Yield Enhancement Network (YEN) which seeks to understand variation in crop yields in the UK and across Europe. The MULTIPLY and Crop Intelligence System projects have been presented to farmers and industry participants at YEN meetings in November 2016 and spring 2017.

The workshop aimed to connect the world’s leading scientists working on hyperspectral data for interpretation of the land surface with international scientists involved in the scientific preparation of several future hyperspectral satellite missions. Amongst others, MULTIPLY was presented as a critical tool to evaluate the added value of hyperspectral data over multispectral Sentinels data. It is a way to integrate information from multiple satellites and an important step forward for understanding land surface and system Earth.

Participants of the ISSI workshop

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 687320